This invention relates to an automatic change gear control device for use in an electromobile.
According to a prior art automatic change gear control device for use in an electromobile, a running condition is determined, based on both a vehicle speed and an output torque of an electric motor, for selecting a gear ratio, so that gear-changing may be made due to the gear ratio thus selected, automatically. In general, when an output torque of an electric motor is increased, with a vehicle speed maintained below a given value, then gears are changed to a large gear ratio.
Included by the cases where an output torque of an electric motor is increased are acceleration during the running on a flat road and a running on an upward slope under an increased load.
However, the prior art change gear control device uses a common output torque of an electric motor, irrespective of the aforesaid classification, thus failing to achieve optimum gear changing, and tends to change gears when the gear changing is not required.
More particularly, with the prior art change gear control device, acceleration may be achieved with ease during the running of a vehicle on a flat road, and this requires frequent changing of gears. This however is not preferable from a viewpoint of drive-feeling. On the other hand, it is desired that upon transition to the running of a vehicle on an upward slope, a large gear ratio be selected rapidly.
In addition, from viewpoints of a total efficiency, it is desired that an electromobile be run at as low r.p.m. of an electric motor, i.e., at as low gear ratio as possible, for minimizing a loss due to rotation of gears.